MultiGroupingPanel on Ext 3.3 beta

I recently tested venky0589's MultiGroupingPanel control on Ext 3.3 beta 2 and found that despite being coded for Ext 2, the control successfully performed multiple grouping on Ext 3.3 beta 2. Thing is, the grouped elements did not expand or contract; when the user attempted to operate them, an error was generated in in file ext-all-debug.js, line 5129: "s.replace is not a function". I believe that some of the standard GridView event handlers were called despite a MultiGroupingView configuration; this error can be reproduced quite easily with Ext 3.3 beta 2, a modestly-configured Apache web server, and the code from venky0589's thread on his seminal grid control. Has anyone managed to get the MultiGroupingPanel control working with Ext 3.3 beta 2?

Solved!

The problem in ExtJS 3.3 happens in the processEvent function of groupingView, which expects getGroupField to return a string with the name of the field. In the Multi-Grouping view the returned value is an array of field names.

I fixed this by copying the processEvent code from GroupingView.js to MultiGroupingView: